Maternal seafood intake and the risk of small for gestational age newborns: a case-control study in Spanish women

Objective To investigate the relationship between seafood consumption during pregnancy and the risk of delivering a small for gestational age (SGA) newborn. Design This case-control study included women with SGA newborns and controls matched 1:1 for maternal age (2 years) and hospital. Setting Five hospitals in Eastern Andalusia, Spain. Participants 518 pairs of pregnant Spanish women. The SGA group included women who delivered SGA newborns: SGA was defined as a birth weight below the 10th percentile of infants at a given gestational age. Controls were women who delivered newborns with adequate birth weights. Interventions We collected data on demographic characteristics, socioeconomic status, toxic habits and diet. Midwives administered a 137-item Food Frequency Questionnaire. Outcome measures We calculated quintiles of seafood intake and applied conditional logistic regression to estimate ORs and 95% CIs. Results Shellfish intake more than once/week yielded a significant protective effect against an SGA newborn (OR 0.25, 95%CI 0.08 to 0.76, after adjusting for energy, educational level, smoking, prepregnancy body mass index, weight and a history of preterm or low birthweight newborn). The risk of an SGA newborn was lower among women who consumed >29g/day fish compared with women who consumed 8g (adjusted OR 0.63, 95%CI 0.41 to 0.98; p=0.025 for a trend). Similarly, the risk of an SGA newborn was lower among women who consumed >1g/day of marine n-3 polyunsaturated fatty acids compared with those who consumed 0.4g/day (adjusted OR 0.58, 95%CI 0.38 to 0.90; p=0.025 for a trend). Conclusion An average seafood intake of at least 29g/day during pregnancy, equivalent to 2-3 servings/week, reduced the risk of an SGA newborn, compared with an average seafood intake of less than 8g/day.